Photonic crystals (PCs) have become attractive optical materials for controlling and manipulating the flow of light. PCs are composed of periodic dielectric or metallic-dielectric structures in one-dimensional (1D), two-dimensional (2D), or three-dimensional (3D) directions, and affect the propagation of electromagnetic waves by defining allowed and forbidden photonic bands. The perfect photonic crystal is quite elegant and beautiful, but it becomes even more useful when a desired defect is introduced into the regular crystal structure. A photon-localized state can be created in the photonic band gap due to a structural defect in the PCs, and the electrical field around the defect can be confined and enhanced. If special materials are contained in the defect, PC structures can be developed as functional photonic devices. Selection from various types of PCs depends on specific applications.
In some cases of controlling light beams which are close to plane waves, a 1D PC (i.e., multilayer structure) is sufficient and preferable due to its simplicity in fabrication. 1D PCs have been used in various applications, such as low-threshold lasers, photodiodes and photodetectors, and optical biosensors. However, in some applications, an additional or separate light detector is required to measure a reflected light signal or an emitted signal, which makes 1D PC based systems complicated and hard to realize compact and integrated systems.